Table 2.

Summary of the included studies with cross-sectional design

Authors	N	Age range & gender	Glioma/tumor subtype	Treatment	Neuropsychological tests	Time between tests	Main findings
Bompaire et al. (2018)44	40	Mean age: 59 years 15 male, 25 female	WHO grade 2 and 3 glioma, GBM	RT with or without CT	MMSE, Digit Span, Fluencies, Dementia Rating Scale, Free Recall Test	FU: >6 months after RT—compared to normative data	Verbal episodic memory and concentration was impaired in (nearly) all patients. In addition, 6 patients had storage impairment. Thirty-four patients had an executive dysfunction, pathological phonemic and semantic fluencies and impaired short-time and working memory.
Boone et al. (2016)2	27	36–51years 17 male, 10 female	AC, ODG, OAC and ependymoma	Surgery, RT, CT	MMSE, RPM, Token Test, BNT, Albert Cancellation Test, ROCF, Digit and Spatial Span, SRT, Doors and People Test, DSST, SCWT, TMT, Categoric and Phonemic Word Fluency Test, Modified Card Sorting Test, BADS	FU: median 3 years after treatment—compared to normative data	In half of the patients psychomotor speed, executive functioning, oral expression, long-term and short-term verbal memory and visual construction were impaired.
Carbo et al. (2017)*,24	28	Mean age: 37 years, 22 male, 6 female	Glioma, cavernoma, cavernous hemangioma, MTS	Surgery	Categoric Fluency, RAVLT, SCWT, LDST	FU:12 months post-surgery—compared to normative data	Patients’ cognitive performance did not change significantly between baseline and post-surgery (group level)
Cayuela et al. (2019)45	48	>18years 30 male, 18 female	WHO grade 2–3 ODG	RT and CT	HVLT, ROCF, COWAT, TMT, MMSE	FU: compared 2–5 years, 6–10 years and >10 years after treatment	Five years after treatment, patients showed severe cognitive impairment. Ten years after treatment, significant more impairment was observed in visual memory and in executive functioning.
Correa et al.46	40	23–59years 25 male 15 female	LGG	RT (12) and CT (5) or no treatment	Digit Span, BTA, TMT A&B, SCWT, Categoric and Phonemic Word Fluency, Auditory Consonant Trigrams, HVLT, BVMT, Grooved Pegboard Test, BNT, Line Orientation Test	FU: median 38 months after diagnosis—compared treatment vs. no treatment	Treated patients scored significantly lower on psychomotor functioning and visual memory than non-treated patients and scored not-significantly lower on attention, executive functioning, verbal memory, and language.
Gondi et al.*,26	18	19–82years 10 male, 8 female	LGG, pituitary adenomas, vestibular schwannomas, meningiomas	Fractioned stereotactic RT	NART, WAIS, BNT, Token Test, Judgment of Line Orientation, Facial Recognition Test, Hooper Visual Organization Test, WMS-III, TMT, SCWT	FU: 12 and 18 months after RT—compared to control group	A correlation was observed between fraction dose to the bilateral hippocampi and memory impairment in the long-term.
Haldbo-Classen et al.47	78	20–79 years 47 male, 31 female	Glioma WHO grade 2–3, meningioma, pituitary adenoma, medulloblastoma	Surgery or biopsy, RT and/or CT	TMT A&B, SCWT, WAIS-IV Coding and Digit Span, HVLT-R, COWAT, PASAT (3 Seconds)	FU: median time since RT 4.6 years—compared to normative data	High RT dose to the left hippocampus was associated with impaired verbal learning and memory. RT dose to the left hippocampus, temporal lobe, frontal lobe and total frontal lobe were associated with verbal fluency impairment and doses to the thalamus and the left frontal lobe with impaired executive functioning.
Klein et al.48	195	24–81years 120 male, 75 female	LGG	Surgery or biopsy with or without RT	NART, Line Bisection Test, Facial Recognition Test, Judgment of Line Orientation Test, LDST, VVLT, WMT, SCWT, Categoric Word Fluency test, CST	FU: 1–22 years after treatment—compared to NHL/CLL and healthy control group	Both irradiated and non-irradiated LGG patients had a significant cognitive decline, suggesting the tumor itself could be responsible. In RT-conditions, fraction dose is responsible for the degree of cognitive decline.
Kocher et al.49	80	28–81 years 50 male, 30 female	GBM, anaplastic AC/ODG	Surgery or biopsy and/or RT and/or CT	TMT A&B, Corsi Block-Tapping Test, DemTect (Supermarket, Number Transcoding, Digit Span, Word List Immediate and Delayed Recall)	FU: 1–114 months after initiation of treatment— compared to control group	Glioma patients performed significantly worse in the majority of cognitive domains. The observed cognitive impairment was mainly associated with reduced connectivity in the left inferior parietal lobule DMN node, resulting in a lowered performance in attention, executive function, language processing, verbal/visual (working) memory, and by the reduced connectivity of the left lateral temporal cortex DMN node, leading to reduced performance in language and verbal episodic memory
Kocher et al.50	121	25–80 years 73 male 48 female	HGG	Surgery or biopsy and/or RT and/or CT	TMT, DemTect (Supermarket, Number Transcoding, Digit Span, Word List Immediate and Delayed Recall)	FU: 1–214 months after therapy—compared to control group	Scores of 9/10 cognitive tests were significantly lower in patients vs. controls, and affected 10%–47% of the patients with a clinically relevant deficit.
Solanki et al.51	9	14–60years 5 male, 4 female	GBM	Surgery and adjuvant CT and RT	Finger Tapping, DSST, Color Trail Test, ANT, N-back Test, Spatial Span Test, Tower of London, AVLT, ROCF	FU: at least 3 years after diagnosis—compared to normative data	Impairment in psychomotor speed (dominant side), information processing speed, sustained attention, planning abilities and long‑term memory was observed.
Taphoorn et al.52	41	18–66years 24 male 17 female	AC, ODG	Surgery (or biopsy) with or without RT	AVLT, WISC Mazes, Categoric Fluency Test, D2-test, Benton Facial Recognition Test, Judgement of Line Orientation Test, SCWT	FU: 12–147 months after diagnosis—compared to control group (NHL/CLL)	More cognitive disturbances in both LGG groups, however no significant differences between the groups with and without RT

Note. WHO = World Health Organization; LGG = low-grade glioma; HGG = high-grade glioma; AC= astrocytoma; OAC= oligo-astrocytoma; ODG= oligodendroglioma; GBM = glioblastoma multiforme; MTS = mesial temporal sclerosis; RT = radiotherapy; CT = chemotherapy; ANT = Auditory naming test; BADS = Behavioural Assessment of the Dysexecutive Syndrome; BNT = Boston Naming Test; BTA = Brief Test of Attention; BVMT = Brief visuospatial memory test; COWAT = Controlled Oral Word Association Test; CST = Concept Shifting Test; DSST = Digit Symbol Substitution test; HVLT(-R) = Hopkins Verbal Learning Test (-Revised); LDST = Letter-digit substitution Test; MMSE = Mini Mental State Exam; NART = National Adult Reading Test; PASAT = Paced Auditory Serial Addition Test; (R)AVLT = Rey Auditory-Verbal Learning Test; ROCF= Rey-Osterrieth Complex Figure; RPM = Raven Progressive Matrices; SCWT = Stroop Color and Word Test; SRT = Buschke Selective Reminding Test; TMT = Trail Making Test; VVLT = Visual verbal learning test; WAIS(-R) = Wechsler Adult Intelligence Scale (Revised); WISC = Wechsler Intelligence Scale for Children; WMS = Wechsler Memory Scale; WMT = working memory task; BL = baseline; FU = follow-up; L= longitudinal design; CS: cross-sectional design; NHL: non-hodgkin lymfoma, CLL: chronic lymphatic leukaemia; DMN = default mode network; *: included in both longitudinal and cross-sectional meta-analyses.